The present invention relates to a machine tool and more particularly to a method for controlling the depth of cut in the radial direction of a rotary cutting tool in a numerically controlled machine tool such as a machining center and an apparatus for carrying out the same.
Hitherto, in a numerically controlled machine tool such as a machining center, when the depth of cut in the radial direction (hereinafter referred to as the "radial depth of cut") of the tip of the cutting tool is to be controlled, it has been a common practice for an eccentric mechanism to be contained within the bore of the main spindle, and the control is carried out by radially shifting the tip of the tool by means of the eccentric mechanism. However, with such a system, since an eccentric bore having a large diameter must be formed substantially over the whole length of the main spindle, not only is its machining difficult, but also the rigidity of the main spindle is decreased. In order to maintain rigidity, the outer diameter of the main spindle must be increased.
Furthermore, since it is impossible for the amount of eccentricity to be made large, there is the problem that the radial depth of cut of the rotary cutting tool is inevitably limited.